Secret Room in Prince Charmings Castle
There is a secret area that is accesible from the room with the dungeon guard (where you kick the prisoners out the window). Do the wall jump until you fall out the big window, you'll fall for a very long time, and then end up in a room that apparently has no exit. The room is full of chickens and has green orbs suspended from the walls. While in this room even the START button won't let you exit the mission.